Lubricating oil additives

ABSTRACT

wherein the polymer carries an inorganic or organic nucleophilic polymerisation terminating group (t), and an initiator group (i) connected to the N atom of a repeat unit (a) or (b), the initiator group (i) being effective to initiate the polymerisation of linear branched or cyclic hydrocarbyl moieties. R1 and R2 are the same or different and comprise a single or a mixture of linear, branched or cyclic hydrocarbyl groups having 1-50 carbon atoms, some or all having 12-50 carbon atoms, or of at least one macro-monomeric hydrocarbyl group with more than 50 carbon atoms.

FIELD OF THE INVENTION

This invention relates to polymeric additives for use in lubricating oilcompositions (lubricants) for lubricating the crankcase of spark-ignitedor compression-ignited internal combustion engines. More especially, theadditives are copolymers of oxazoline monomers and oxazine monomers thatprovide friction modifying properties to lubricating oils. The additivesalso do not adversely affect lubricant viscosity.

BACKGROUND OF THE INVENTION

There is much interest in improving the fuel economy of gasoline anddiesel engines. This can be done, through the lubricant engine oil, byreducing the friction contribution either of the bulk fluid (by loweringthe oil viscosity) or improving the friction of the contacting parts byinclusion of friction modifier additives.

There is therefore interest in additives with low friction properties inlow viscosity oils.

Dispersant viscosity modifier (DVM) additives are known to providefriction modification. Examples known in the art, based on polymertechnology, are olefin copolymers (OCP) and methacrylate copolymers. Aproblem with such additives especially in applications which requireultra-low viscosity lubricating fluids such as 0W-8, 0W-16, 0W-20 istheir high thickening efficiencies.

Poly(2-oxazoline)s are known in the art. For example, the art describesthe living cationic ring-opening polymerization of 2-oxazolines. SeeHoogenboom et al., Angew. Chem. Int. Ed 2009, 48, 7978-7994. U.S. Pat.No. 4,120,804 describes the use of short oligomers of poly(2-oxazoline)shaving 2 to 15 repeating units as dispersants to prevent or reduce theformation of sludges, or to neutralise acidic components etc. inlubricating oils. The polymerisation initiator is a polymeric materialof molecular weight equal to or greater than 250 and the oxazoline is2-substituted with a hydrocarbyl group of 1-18 carbon atoms. No mentionis made of friction modification, or of lubricant viscosity impact.

Polyoxazines are also known in the art see Hoogenboom et al., Macromol.,2011, 3420. U.S. Pat. No. 4,001,147 describes certain polyoxazines asuseful to remove phenolic compounds from aqueous waste streams.

U.S. Pat. No. 5,439,978 describes the use of both oxazoline andoxazine-based copolymers as additives to render electrically conductive,nonconductive materials such as plastics.

SUMMARY OF THE INVENTION

In a first aspect, the invention provides a lubricating compositioncomprising a major amount of an oil of lubricating viscosity and 0.01 to25 percent by mass, based to on the mass of the composition of anoil-soluble copolymer comprising units (a) and units (b):

—N(COR¹)CH₂CH₂—  (a)

—N(COR²)CH₂CH₂CH₂—  (b)

wherein the polymer carries an inorganic or organic nucleophilicpolymerisation terminating group (t), and an initiator group (i)connected to the N atom of a repeat unit (a) or (b), the initiator group(i) being effective to initiate the polymerisation of linear, branchedor cyclic hydrocarbyl moieties; and

wherein R¹ and R² are the same or different and comprise a single or amixture of linear, branched or cyclic hydrocarbyl groups having 1-50carbon atoms, some or all having 12-50 carbon atoms, or of at least onemacro-monomeric hydrocarbyl group with more than 50 carbon atoms

In a second aspect, the invention provides a method of lubricating thecrankcase of an internal combustion engine comprising operating theengine and lubricating the crankcase with a lubricating composition ofthe first aspect of the invention in the form of a crankcase lubricant.

In a third aspect, the invention provides the use of an oil-solublecopolymer comprising units (a) and units (b):

—N(COR¹)CH₂CH₂—  (a)

—N(COR²)CH₂CH₂CH₂—  (b)

wherein the polymer carries an inorganic or organic nucleophilicpolymerisation terminating group (t), and an initiator group (i)connected to the N atom of a repeat unit (a) or (b), the initiator group(i) being effective to initiate the polymerisation of linear, branchedor cyclic hydrocarbyl moieties; and

wherein R¹ and R² are the same or different and comprise a single or amixture of linear, branched or cyclic hydrocarbyl groups having 1-50carbon atoms, some or all having 12-50 carbon atoms, or of at least onemacro-monomeric hydrocarbyl group with more than 50 carbon atoms, in alubricant for an internal combustion engine to provide the lubricant, inoperation of the engine, with friction reducing properties.

Units (a) of the copolymer are derived from 2-substituted-2-oxazolinemonomers and units (b) are derived from 2-substituted-2-oxazinemonomers. The copolymers of the invention may be made by living cationicring-opening polymerization of the two types of monomer.

Preferably units (a) comprise from 1 to 99 mol % of the copolymer andunits (b) comprise from 1 to 99 mol % of the copolymer. More preferably,units (a) comprise from 10 to 90 mol % of the copolymer and units (b)comprise from 10 to 90 mol % of the copolymer. For example, thecopolymer may comprise from 20 to 80 mol % or 30 to 70 mol % or 40 to 60mol % of units (a) and from 20 to 80 mol % or 30 to 70 mol % or 40 to 60mol % of units (b). In a preferred embodiment the copolymer comprises 50mol % of units (a) and 50 mol % of units (b).

in some embodiments, the copolymer is a statistical copolymer or arandom copolymer, In other embodiments, the copolymer is an alternatingcopolymer, a periodic copolymer or a block copolymer.

The copolymer may have linear architecture or may have a branched orstar architecture.

A general process for making statistical or random copolymers comprisespolymerizing a mixture of at least one 2-substituted-2-oxazoline and atleast one at least one 2-substituted-2-oxazine with an initiator.

A general process for making block copolymers comprises polymerising afirst 2-substituted-2-oxazine monomer with an initiator to make a firstpolymeric block and then polymerising with a 2-substituted-2-oxazolinemonomer to make a second polymeric block. Further blocks may be providedif required.

Examples of these processes will be provided in this specification.

DETAILED DESCRIPTION OF THE INVENTION Definitions

In this specification, the following words and expressions, if and whenused, have the meaning given below:

“active ingredients” or “(a.i.)” refers to additive material that is notdiluent or solvent;

“comprising” or any cognate word specifies the presence of statedfeatures, steps, or integers or components, but does not preclude thepresence or addition of one or more other features, steps, integers,components or groups thereof. The expressions “consists of” or “consistsessentially of” or cognates may be embraced within “comprises” or anycognate word. The expression “consists essentially of” permits inclusionof substances not materially affecting the characteristics of thecomposition to which it applies. The expression “consists of” orcognates means only the stated features, steps, integers components orgroups thereof are present to which the expression refers;

“hydrocarbyl” means a chemical group of a compound that containshydrogen and carbon atoms and that is bonded to the remainder of thecompound directly via a carbon atom. The group may contain one or moreatoms other than carbon and hydrogen (“hetero atoms”) provided they donot affect the essentially hydrocarbyl nature of the group. Thoseskilled in the art will be aware of suitable groups (e.g., halo,especially chloro and fluoro, amino, alkoxyl, mercapto, alkylmercapto,nitro, nitroso, sulfoxy, etc.). The group may be unsaturated, and/or maybe polymeric. Preferably, the hydrocarbyl group consists essentially ofhydrogen and carbon atoms. More preferably, the hydrocarbyl groupconsists of hydrogen and carbon atoms and so is a hydrocarbon group.Preferably, the hydrocarbyl group is an aliphatic hydrocarbyl group,such as an alkyl group;

“oil-soluble” or “oil-dispersible”, or cognate terms, used herein do notnecessarily indicate that the compounds or additives are soluble,dissolvable, miscible, or are capable of being suspended in the oil inall proportions, These do mean, however, that they are, for example,soluble or stably dispersible in oil to an extent sufficient to exerttheir intended effect in the environment in which the oil is employed.Moreover, the additional incorporation of other additives may alsopermit incorporation of higher levels of a particular additive, ifdesired;

-   -   “ashless” in relation to an additive means the additive does not        include a metal;    -   “ash-containing” in relation to an additive means the additive        includes a metal;    -   “major amount” means in excess of 50 mass % of a composition or        mixture;    -   “minor amount” means 50 mass % or less of a composition or        mixture;    -   “effective amount” in respect of an additive means an amount of        such an additive in the composition (e.g. an additive        concentrate) that is effective to provide, and provides, the        desired technical effect;    -   “ppm” means parts per million by mass, based on the total mass        of the composition;    -   “metal content” of a composition or of an additive component,        for example molybdenum content or total metal content of the        additive concentrate (i.e. the sum of all individual metal        contents), is measured by ASTM D5185;    -   “TBN” in relation to an additive component or of a composition,        means total base number (mg KOH/g) as measured by ASTM D2896;    -   “KV₁₀₀” means kinematic viscosity at 100° C. as measured by ASTM        D445;    -   HTHS means High Temperature High Shear at 150° C. as measured        by-CEC-L-36-A-90.    -   “phosphorus content” is measured by ASTM D5185;    -   “sulfur content” is measured by ASTM D2622;    -   “sulfated ash content” is measured by ASTM D874;    -   M_(n) means number average molecular weight as measured by Gel        Permeation Chromatography with reference to linear narrow        poly(methylmethacrylate) standards in the range of 550 to        600,000 g/mol;    -   M_(w) means weight average molecular weight as measured by Gel        Permeation Chromatography with reference to linear narrow        poly(methylmethacrylate) standards in the range of 550 to        600,000 g/mol;    -   “dispersity” means M_(w)/M_(n), (denoted by Ð)        Also it will be understood that various components used,        essential as well as optimal and customary, may react under        condition of formulation, storage and use and that the invention        also provides the product(s) obtainable or obtained by any such        reaction.        Further it is understood that any upper and lower quality, range        or ratio limits set forth herein may be independently combined.

Copolymers

The copolymers useful in the invention are copolymers, i.e. polymersderived from more than one species of monomer, They are formed from atleast one 2-substituted-2-oxazoline monomer and at least one at leastone 2-substituted-2-oxazine monomer.

As examples of copolymers there may be mentioned statistical copolymerswhich are formed where the polymerisation follows a known statisticalrule, for example Bemouillian statistics or Markovian statistics. Astatistical polymer where the probability of finding a particular typeof monomer residue at any particular point in the polymer chain isindependent of the types of surrounding monomers can be referred to as arandom copolymer. Statistical and random copolymers may be distinguishedfrom more ordered polymer types such as alternating copolymers, periodiccopolymers and block copolymers.

Block copolymers, i.e. in which two or more polymer (e.g. homopolymers)sub-units are linked by covalent bonds (e.g. as di- or tri-blocks), arenoteworthy in the context of this invention. The blocks in any blockcopolymer may be of equal size or of different sizes and thearchitecture of the copolymers can vary. For example, block copolymersmay have only a single block of each monomer (i.e. in a ‘AB’arrangement) or multiple blocks of each monomer (i.e. in an ‘ABABAB . .. ’ arrangement) where blocks ‘A’ and ‘B’ may be the same size or ofdifferent sizes.

Also noteworthy are branched polymers, in particular star polymers whereseveral (three or more) linear polymer chains (or “arms”) are covalentlybonded to a central core.

Any cationic specks is capable of initiating polymerization of2-oxazolines or 2-oxazines. Examples include H⁺ (from HCl or otheracids); R⁺ (for example from alkyl halides such as RI or RBr); and metalcations and salts (e.g. Zr⁴⁺). Any nucleophilic species is capable ofterminating the polymerization (e.g. OH⁻ from atmospheric water,OTs⁻(tosylate), H₂NR, HSR). Other suitable initiator groups (i) andterminating groups (t) will be known to those skilled in the art.

When a star architecture is required, the copolymer may be prepared byuse of a multifunctional initiator; by cross linking; or by use of amultifunctional terminator or coupling.

Preferably, the copolymer has a number average molecular weight (Mn) of2,000-500,000 g/mol. More preferably, the copolymer has a number averagemolecular weight (Mn) of 4,000-100,000 g/mol. Even more preferably, thecopolymer has a number average molecular weight (Ma) of 6,000-50,000g/mol, for example 8,000-20,000 g/mol. All molecular weights are asmeasured by Gel Permeation Chromatography with reference to linearnarrow poly(methylmethacrylate) standards in the range of 550 to 600,000g/mol.

In an embodiment, the copolymer has a star architecture with three ormore arms, and a number average molecular weight (Mn) of 10,000-500,000g/mol, R¹ and/or R² having at least some groups of 12-50 carbon atoms inat least one arm. All molecular weights are as measured by GelPermeation Chromatography with reference to linear narrowpoly(methylmethacrylate) standards in the range of 550 to 600,000 g/mol.

When R¹ and/or R² is a macro-monomeric hydrocarbyl group, it may beprovided via

-   -   a) polymerization from a reactive group in an R¹ or R²        precursor; or    -   b) incorporation of a pre-formed macro-monomeric in hydrocarbyl        group in an R¹ or R² precursor.

The significance of the presence of R¹ and/or R² groups having 12-50carbon atoms is to make the copolymers sufficiently oleophilic to confersolubility in a polar media such as base oil.

Preferably R¹ and R² are the same or different and contain 1 to 36, morepreferably 1 to 20 carbon atoms, provided that some or all of the groupsR¹ or R² have 12 to 75, preferably 12 to 50, for example 12 to 36 carbonatoms.

As examples of the number of carbon atoms in the R¹ and R² groups, theremay be mentioned 1, 2, 8, 12, 17 and 24.

In one embodiment one of groups R¹ and R² comprise unsaturatedhydrocarbyl groups having between 8 and 20 carbon atoms in which casethe other group is saturated. In another embodiment, both of groups R¹and R² comprise unsaturated hydrocarbyl groups having between 8 and 20carbon atoms. Preferably, at least 5% of the total number of either orboth of the groups R¹ and R² in the polymer comprise unsaturatedhydrocarbyl groups having between 8 and 20 carbon atoms. Morepreferably, at least 10%, or 20% or 30% or 40% or 50% of the totalnumber of either or both of the groups R¹ and R² in the polymer compriseunsaturated hydrocarbyl groups having between 8 and 20 carbon atoms.Most preferably, at least 60% or 70% of the total number of either orboth of the groups R¹ and R² in the polymer comprise unsaturatedhydrocarbyl groups having between 8 and 20 carbon atoms.

Preferably, at least 5% of the total number of either or both of thegroups R¹ and R² in the polymer comprise unsaturated hydrocarbyl groupshaving between 15 and 20 carbon atoms. More preferably, at least 10%, or20% or 30% or 40% or 50% of the total number of either or both of thegroups R¹ and R² in the polymer comprise unsaturated hydrocarbyl groupshaving between 15 and 20 carbon atoms. Most preferably, at least 60% or70% of the total number of either or both of the groups R¹ and R² in thepolymer comprise unsaturated hydrocarbyl groups having between 15 and 20carbon atoms,

Preferably, at least 5% of the total number of either or both of thegroups R¹ and R² in the polymer comprise unsaturated hydrocarbyl groupshaving 17 carbon atoms. More preferably, at least 10%, or 20% or 30% or40% or 50% or 60% of the total number of either or both of the groups R¹and R² in the polymer comprise unsaturated hydrocarbyl groups having 17carbon atoms. Even more preferably, at least 70% of the total number ofeither or both of the groups R¹ and R² in the polymer compriseunsaturated hydrocarbyl groups having 17 carbon atoms.

In an embodiment, groups R¹ and R² do not contain any hetero-atoms, i.e.are hydrocarbon groups. Preferably groups R¹ and R² are hydrocarbongroups.

In preferred embodiments, at least 50% of the total number of either orboth of the groups R¹ and R² in the polymer comprise singly, doubly ortriply-unsaturated C₁₇ alkenyl groups or any mixture thereof. Morepreferably, at least 60% of the total number is of either or both of thegroups R¹ and R² in the polymer comprise singly, doubly ortriply-unsaturated C₁₇ alkenyl groups or any mixture thereof. Even morepreferably, at least 70% of the total number of either or both of thegroups R¹ and R² in the polymer comprise singly, doubly ortriply-unsaturated C₁₇ alkenyl groups or any mixture thereof.

In particularly preferred embodiments, either or both of groups R¹ andR² comprise a mixture of singly, doubly or triply-unsaturated C₁₇alkenyl groups which mixture predominates in singly, anddoubly-unsaturated C₁₇ alkenyl groups. Such mixtures may comprise smallamounts of smaller and longer molecules.

Suitable sources for mixtures of groups for either or both of R¹ and R²include 2-oxazolines and 2-oxazines derived from natural fatty acidssuch as tall oil fatty acid (TOFA) and rape-seed oil fatty acid. Othersuitable sources will be known to those skilled in the art.

In an embodiment, R¹ and/or R² may contain hetero atoms (such as N, O,S, P, B, Si, F, Cl, Br, I). As discussed hereinabove, the term‘hydrocarbyl’ when applied to R¹ and R² permits the presence of alimited number of hetero atoms and so is not limited to groups whichcontain carbon and hydrogen only.

Lubricating Compositions

Lubricating compositions of the invention may be lubricants suitable foruse as motor vehicle motor oils comprising a major amount of oil oflubricating viscosity and minor amounts of performance-enhancingadditives, including the polymeric material. The lubricating compositionmay also be in the form of an additive concentrate for blending with oilof lubricating viscosity to make a final lubricant.

Preferably the lubricating compositions of the invention will contain0.01 to 25 percent by mass, based on the mass of the composition of theoil-soluble copolymer, more preferably 0.01 to 10, for example up to0.5, 1, 2, 3, 4 or 5 percent by mass, based to on the mass of thecomposition. When in the form of an additive concentrate, typically theoil-soluble copolymer will be present in an oil of lubricating viscosityin an amount of 30 to 50 percent by mass, based on the mass of thecomposition.

The oil of lubricating viscosity (sometimes referred to as “base stock”or “base oil”) is the primary liquid constituent of a lubricant, intowhich additives and possibly other oils are blended, for example toproduce a final lubricant (or lubricant composition). A base oil, whichis useful for making additive concentrates as well as for makinglubricating oil compositions therefrom, may be selected from naturaloils (vegetable, animal or mineral) and synthetic lubricating oils andmixtures thereof.

Definitions for the base stocks and base oils in this invention are thesame as those found in the American Petroleum Institute (API)publication “Engine Oil Licensing and Certification System”, IndustryServices Department, Fourteenth Edition, December 1996, Addendum 1,December 1998, which categorizes base stocks as follows:

-   -   a) Group I base stocks contain less than 90 percent saturates        and/or greater than 0.03 percent sulphur and have a viscosity        index greater than or equal to 80 and less than 120 using the        test methods specified in Table E-1.    -   b) Group II base stocks contain greater than or equal to 90        percent saturates and less than or equal to 0.03 percent sulphur        and have a viscosity index greater than or equal to 80 and less        than 120 using the test methods specified in Table E-1.    -   c) Group III base stocks contain greater than or equal to 90        percent saturates and less than or equal to 0.03 percent sulphur        and have a viscosity index greater than or equal to 120 using        the test methods specified in Table E-1.    -   d) Group IV base stocks are polyalphaolefins (PAO).    -   e) Group V base stocks include all other base stocks not        included in Group I, II, III, or IV.

Typically, the base stock has a viscosity preferably of 3-12, morepreferably 4-10, most preferably 4.5-8, mm²/s at 100° C.

TABLE E-1 Analytical Methods for Base Stock Property Test MethodSaturates ASTM D 2007 Viscosity Index ASTM D 2270 Sulphur ASTM D 2622ASTM D 4294 ASTM D 4927 ASTM D 3120

Preferably, the oil of lubricating viscosity comprises greater than orequal to 10, more preferably greater than or equal to 20, even morepreferably greater than or equal to 25, even more preferably greaterthan or equal to 30, even more preferably greater than or equal to 40,even more preferably greater than or equal to 45, mass % of a Group IIor Group III base stock, based on the total mass of the oil oflubricating viscosity. Even more preferably, the oil of lubricatingviscosity comprises greater than 50, preferably greater than or equal to60, more preferably greater than or equal to 70, even more preferablygreater than or equal to 80, even more preferably greater than or equalto 90, mass % of a Group II or Group III base stock, based on the totalmass of the oil of lubricating viscosity. Most preferably, the oil oflubricating viscosity consists essentially of a Group II and/or GroupIII base stock. In some embodiments the oil of lubricating viscosityconsists solely of Group II and/or Group III base stock. In the lattercase it is acknowledged that additives included in the lubricating oilcomposition may comprise a carrier oil which is not a Group II or GroupIII base stock.

Other oils of lubricating viscosity that may be included in thelubricating oil composition are detailed as follows:

Natural oils include animal and vegetable oils (e.g. castor and lardoil), liquid petroleum oils and hydro refined, solvent-treated minerallubricating oils of the paraffinic, naphthenic and mixedparaffinic-naphthenic types. Oils of lubricating viscosity derived fromcoal or shale are also useful base oils.

Synthetic lubricating oils include hydrocarbon oils such as polymerizedand interpolymerized olefins (e.g. polybutylenes, polypropylenes,propylene-isobutylene copolymers, chlorinated polybutylenes,poly(1-hexenes), poly(1-octenes), poly(1-decenes)); alkylbenzenes (e.g.dodecylbenzenes, tetradecylbenzenes, dinonylbenzeries,di(2-ethylhexyl)benzeries); polyphenols (e.g. biphenyls, terphenyls,alkylated polyphenols); and alkylated diphenyl ethers and alkylateddiphenyl sulfides and the derivatives, analogues and homologues thereof.

Another suitable class of synthetic lubricating oil comprises the estersof dicarboxylic acids (e.g. phthalic acid, succinic acid, alkyl succinicacids and alkenyl succinic acids, maleic acid, azelaic acid, subericacid, sebasic acid, fumaric acid, adipic acid, linoleic acid dimer,malonic acid, alkylmalonic acids, alkenyl malonic acids) with a varietyof alcohols (e.g. butyl alcohol, hexyl alcohol, dodecyl alcohol,2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether,propylene glycol). Specific examples of these esters include dibutyladipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctylsebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate,didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester oflinolreic acid dimer, and the complex ester formed by reacting one moleof sebacic acid with two moles of tetraethylene glycol and two moles of2-ethylhexanoic acid.

Esters useful as synthetic oils also include those made from C₅ to C₁₂monocarboxylic acids and polyols, and polyol ethers such as neopentylglycol, trimethylolpropane, pentaerythritol, dipentaerythritol andtripentaerythritol.

Unrefined, refined and re-refined oils can be used in the compositionsof the present invention. Unrefined oils are those obtained directlyfrom a natural or synthetic source without further purificationtreatment. For example, a shale oil obtained directly from retortingoperations, a petroleum oil obtained directly from distillation or esteroil obtained directly from an esterification process and used withoutfurther treatment would be unrefined oil. Refined oils are similar tothe unrefined oils except they have been further treated in one or morepurification steps to improve one or more properties. Many suchpurification techniques, such as distillation, solvent extraction, acidor base extraction, filtration and percolation, are known to thoseskilled in the art. Re-refined oils are obtained by processes similar tothose used to obtain refined oils applied to refined oils that have beenalready used in service. Such re-refined oils are also known asreclaimed or reprocessed oils and often are additionally processed bytechniques for treating spent additive and oil breakdown products.

Other examples of base oil are gas-to-liquid (“GTL”) base oils, i.e. thebase oil may be an oil derived from Fischer-Tropsch synthesisedhydrocarbons made from synthesis gas containing H₂ and CO using aFischer-Tropsch catalyst. These hydrocarbons typically require furtherprocessing in order to be useful as a base oil. For example, they may,by methods known in the art, be hydroisomerized; hydrocracked andhydroisomerized; dewaxed; or hydroisomerized and dewaxed.

The oil of lubricating viscosity may also comprise a Group I, Group IVor Group V base stocks or base oil blends of the aforementioned basestocks.

The lubricating compositions of the present invention preferablycomprise at least 60% by weight, for example 70% by weight or more of anoil of lubricating viscosity, based on the weight of the composition.

Co-Additives

The lubricating oil compositions of all aspects of the present inventionmay further comprise one or more phosphorus-containing compounds;oxidation inhibitors or anti-oxidants; dispersants; metal detergents;and other co-additives, provided they are different from the oil-solublecopolymer comprising units (a) and units (b). These will be discussed inmore detail below.

Suitable phosphorus-containing compounds include dihydrocarbyldithiophosphate metal salts, which are frequently used as antiwear andantioxidant agents. The metal is preferably zinc, but may be an alkalior alkaline earth metal, or aluminium, lead, tin, molybdenum, manganese,nickel or copper. The zinc salts are most commonly used in lubricatingoil in amounts of 0.1 to 10, preferably 0.2 to 2 mass %, based upon thetotal weight of the lubricating oil composition. They may be prepared inaccordance with known techniques by first forming a dihydrocarbyldithiophosphoric acid (DDPA), usually by reaction of one or more alcoholor a phenol with P₂S₅, and then neutralizing the formed DDPA with a zinccompound. For example, a dithiophosphoric acid may be made by reactingmixtures of primary and secondary alcohols. Alternatively, multipledithiophosphoric acids can be prepared where the hydrocarbyl groups onone are entirely secondary in character and the hydrocarbyl groups onthe others are entirely primary in character. To make the zinc salt, anybasic or neutral zinc compound could be used but the oxides, hydroxidesand carbonates are most generally employed. Commercial additivesfrequently contain an excess of zinc due to the use of an excess of thebasic zinc compound in the neutralization reaction.

The preferred zinc dihydrocarbyl dithiophosphates are oil-soluble saltsof dihydrocarbyl dithiophosphoric acids and may be represented by thefollowing formula:

wherein R and R′ may be the same or different hydrocarbyl radicalscontaining from 1 to 18, preferably 2 to 12, carbon atoms and includingradicals such as alkyl, alkenyl, aryl, arylalkyl, alkaryl andcycloaliphatic radicals. Particularly preferred as R and R′ groups arealkyl groups of 2 to 8 carbon atoms. Thus, the radicals may, forexample, be ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl,amyl, n-hexyl, i-hexyl, n-octyl, decyl, dodecyl, octadecyl,2-ethylhexyl, phenyl, butylphenyl, cyclohexyl, methylcyclopentyl,propenyl, butentyl. In order to obtain oil solubility, the total numberof carbon atoms (i.e. R and R′) in the dithiophosphoric acid willgenerally be 5 or greater. The zinc dihydrocarbyl dithiophosphate (ZDDP)can therefore comprise zinc dialkyl dithiophosphates. Lubricating oilcompositions of the present invention suitably may have a phosphoruscontent of no greater than about 0.08 mass % (800 ppm). Preferably, inthe practice of the present invention, ZDDP is used in an amount closeor equal to the maximum amount allowed, preferably in an amount thatprovides a phosphorus content within 100 ppm of the maximum allowableamount of phosphorus. Thus, lubricating oil compositions useful in thepractice of the present invention preferably contain ZDDP or otherzinc-phosphorus compounds, in an amount introducing from 0.01 to 0.08mass % of phosphorus, such as from 0.04 to 0.08 mass % of phosphorus,preferably, from 0.05 to 0.08 mass % of phosphorus, based on the totalmass of the lubricating oil composition.

Oxidation inhibitors or antioxidants reduce the tendency of mineral oilsto deteriorate in service. Oxidative deterioration can be evidenced bysludge in the lubricant, varnish-like deposits on the metal surfaces,and by viscosity growth. Such oxidation inhibitors include hinderedphenols, alkaline earth metal salts of alkylphenolthioesters havingpreferably C₅ to C₁₂ alkyl side chains, calcium to nonylphenol sulfide,oil soluble phenates and sulfurized phenates, phosphosulfurized orsulfurized hydrocarbons or esters, phosphorous esters, metalthiocarbamates, oil soluble copper compounds as described in U.S. Pat.No. 4,867,890, and molybdenum-containing compounds.

Aromatic amines having at least two aromatic groups attached directly tothe nitrogen constitute another class of compounds that is frequentlyused for antioxidancy. Typical oil-soluble aromatic amines having atleast two aromatic groups attached directly to one amine nitrogencontain from 6 to 16 carbon atoms. The amines may contain more than twoaromatic groups. Compounds having a total of at least three aromaticgroups in which two aromatic groups are linked by a covalent bond or byan atom or group (e.g., an oxygen or sulfur atom, or a —CO—, —SO₂— oralkylene group) and two are directly attached to one amine nitrogen arealso considered aromatic amines having at least two aromatic groupsattached directly to the nitrogen. The aromatic rings are typicallysubstituted by one or more substituents selected from alkyl, cycloalkyl,alkoxy, aryloxy, acyl, acylamino, hydroxy, and nitro groups. The amountof any such oil soluble aromatic amines having at least two aromaticgroups attached directly to one amine nitrogen should preferably notexceed 0.4 mass %.

A dispersant is an additive whose primary function is to hold solid andliquid contaminations in suspension, thereby passivating them andreducing engine deposits at the same time as reducing sludgedepositions. For example, a dispersant maintains in suspensionoil-insoluble substances that result from oxidation during use of thelubricant, thus preventing sludge flocculation and precipitation ordeposition on metal parts of the engine.

Dispersants in this invention are preferably “ashless”, as mentionedabove, being non-metallic organic materials that form substantially noash on combustion, in contrast to metal-containing and hence ash-formingmaterials. They comprise a long hydrocarbon chain with a polar head, thepolarity being derived from inclusion of e.g. an O, P, or N atom. Thehydrocarbon is an oleophilic group that confers oil-solubility, having,for example 40 to 500 carbon atoms. Thus, ashless dispersants maycomprise an oil-soluble polymeric backbone.

A preferred class of olefin polymers is constituted by polybutenes,specifically polyisobutenes (PIB) or poly-n-butenes, such as may beprepared by polymerization of a C₄ refinery stream.

Dispersants include, for example, derivatives of long chainhydrocarbon-substituted carboxylic acids, examples being derivatives ofhigh molecular weight hydrocarbyl-substituted succinic acid. Anoteworthy group of dispersants is constituted byhydrocarbon-substituted succinimides, made, for example, by reacting theabove acids (or derivatives) with a nitrogen-containing compound,advantageously a polyalkylene polyamine, such as a polyethylenepolyamine. Particularly preferred are the reaction products ofpolyalkylene polyamines with alkenyl succinic anhydrides, such asdescribed in U.S. Pat. Nos. 3,202,678; 3,154,560; 3,172,892; 3,024,195;3,024,237, 3,219,666; and 3,216,936, that may be post-treated to improvetheir properties, such as borated (as described in U.S. Pat. Nos.3,087,936 and 3,254,025), fluorinated or oxylated. For example, borationmay be accomplished by treating an acyl nitrogen-containing dispersantwith a boron compound selected from boron oxide, boron halides, boronacids and esters of boron acids.

Preferably, the dispersant, if present, is a succinimide-dispersantderived from a polyisobutene of number average molecular weight in therange of 1000 to 3000, preferably 1500 to 2500, and of moderatefunctionality. The succinimide is preferably derived from highlyreactive polyisobutene.

Another example of dispersant type that may be used is a linked aromaticcompound such as described in EP-A-2 090 642.

A detergent is an additive that reduces formation of piston deposits,for example high-temperature varnish and lacquer deposits in engines; itnormally has acid-neutralising properties and is capable of keepingfinely-divided solids in suspension.

Most detergents are based on metal “soaps”, that is metal salts ofacidic organic compounds.

Detergents generally comprise a polar head with a long hydrophobic tail,the polar head comprising the metal salt of the acidic organic compound.The salts may contain a substantially stoichiometric amount of the metalwhen they are usually described as normal or neutral salts and wouldtypically have a total base number or TBN at 100% active mass (as may bemeasured by ASTM D2896) of from 0 to 80. Large amounts of a metal basecan be included by reaction of an excess of a metal compound, such as anoxide or hydroxide, with an acidic gas such as carbon dioxide.

The resulting overbased detergent comprises neutralised detergent as anouter layer of a metal base (e.g. carbonate) micelle. Such overbaseddetergents may have a TBN at 100% active mass of 150 or greater, andtypically of from 200 to 500 or more.

Suitably, detergents that may be used include oil-soluble neutral andoverbased sulfonates, phenates, sulfurised phenates, thiophosphonates,salicylates and naphthenates and other oil-soluble carboxylates of ametal, particularly alkali metal or alkaline earth metals, e.g. Na, K,Li, Ca and Mg. The most commonly-used metals are Ca and Mg, which mayboth be present in detergents used in lubricating compositions, andmixtures of Ca and/or Mg with Na. Detergents may be used in variouscombinations.

Additional additives may be incorporated into the compositions of theinvention to enable particular performance requirements to be met.Examples of such additives which may be included in the lubricating oilcompositions of the present invention are metal rust inhibitors,viscosity index improvers, corrosion inhibitors, oxidation inhibitors,other friction modifiers, anti-foaming agents, anti-wear agents and pourpoint depressants. Some are discussed in further detail below.

Friction modifiers and fuel economy agents that are compatible with theother ingredients of the final oil may also be included. Examples ofsuch materials include glyceryl monoesters of higher fatty acids, forexample, glyceryl mono-oleate; esters of long chain polycarboxylic acidswith diols, for example, the butane diol ester of a dimerizedunsaturated fatty acid; and alkoxylated alkyl-substituted mono-amines,diamines and alkyl ether amines, for example, ethoxylated tallow amineand ethoxylated tallow ether amine.

Other known friction modifiers comprise oil-soluble oregano molybdenumcompounds. Such oregano-molybdenum friction modifiers also provideantioxidant and antiwear credits to a lubricating oil composition.Examples of such oil-soluble oregano-molybdenum compounds includedithiocarbamates, dithiophosphates, dithiophosphinates, xanthates,thioxanthates, sulfides, and the like, and mixtures thereof.Particularly preferred are molybdenum dithiocarbamates,dialkyldithiophosphates, alkyl xanthates and alkylthioxanthates,

Additionally, the molybdenum compound may be an acidic molybdenumcompound. These compounds will react with a basic nitrogen compound asmeasured by ASTM test D-664 or D-2896 titration procedure and aretypically hexavalent. Included are molybdic acid, ammonium molybdate,sodium molybdate, potassium molybdate, and other alkali metal molybdatesand other molybdenum salts, e.g., hydrogen sodium molybdate, MoOCl₄,MoO₂Br₂, Mo₂O₃Cl₆, molybdenum trioxide or similar acidic molybdenumcompounds.

Among the molybdenum compounds useful in the compositions of thisinvention are oregano-molybdenum compounds of the formula

Mo(R″OCS₂)₄ and

Mo(R″SCS₂)₄

wherein R″ is an oregano group selected from the group consisting ofalkyl, aryl, aralkyl and alkoxyalkyl, generally of from 1 to 30 carbonatoms, and preferably 2 to 12 carbon atoms and most preferably alkyl of2 to 12 carbon atoms. Especially preferred are thedialkyldithiocarbamates of molybdenum.

Another group of oregano-molybdenum compounds useful in the lubricatingcompositions of this invention are trinuclear molybdenum compounds,especially those of the formula Mo₃S_(k)L_(n)Q_(z) and mixtures thereofwherein the L are independently selected ligands having oregano groupswith a sufficient number of carbon atoms to render the compound solubleor dispersible in the oil, n is from 1 to 4, k varies from 4 to 7, Q isselected from the group of neutral electron donating compounds such aswater, amines, alcohols, phosphines, and ethers, and z ranges from 0 to5 and includes non-stoichiometric values. At least 21 carbon atomsshould be present among all the ligand oregano groups, such as at least25, at least 30, or at least 35, carbon atoms.

Lubricating oil compositions useful in all aspects of the presentinvention preferably contain at least 10 ppm, at least 30 ppm, at least40 ppm and more preferably at least 50 ppm molybdenum. Suitably,lubricating oil compositions useful in all aspects of the presentinvention contain no more than 1000 ppm, no more than 750 ppm or no morethan 500 ppm of molybdenum. Lubricating oil compositions useful in allaspects of the present invention preferably contain from 10 to 1000,such as 30 to 750 or 40 to 500, ppm of molybdenum (measured as atoms ofmolybdenum).

The viscosity index of the base stock is increased, or improved, byincorporating therein certain polymeric materials that function asviscosity modifiers (VM) or to viscosity index improvers (VII).Generally, polymeric materials useful as viscosity modifiers are thosehaving number average molecular weights (Mn) of from 5,000 to 250,000,preferably from 15,000 to 200,000, more preferably from 20,000 to150,000. These viscosity modifiers can be grafted with graftingmaterials such as, for example, maleic anhydride, and the graftedmaterial can be reacted with, for example, amines, amides,nitrogen-containing heterocyclic compounds or alcohol, to formmultifunctional viscosity modifiers (dispersant-viscosity modifiers).

Polymers prepared with diolefins will contain ethylenic unsaturation,and such polymers are preferably hydrogenated. When the polymer ishydrogenated, the hydrogenation may be accomplished using any of thetechniques known in the prior art. For example, the hydrogenation may beaccomplished such that both ethylenic and aromatic unsaturation isconverted (saturated) using methods such as those taught, for example,in U.S. Pat. Nos. 3,113,986 and 3,700,633 or the hydrogenation may beaccomplished selectively such that a significant portion of theethylenic unsaturation is converted while little or no aromaticunsaturation is converted as taught, for example, in U.S. Pat. Nos.3,634,595; 3,670,054; 3,700,633 and Re 27,145. Any of these methods canalso be used to hydrogenate polymers containing only ethylenicunsaturation and which are free of aromatic unsaturation.

Pour point depressants (PPD), otherwise known as lube oil flow improvers(LOFIs) lower the lowest temperature at which the lube flows. Comparedto VM, LOFIs generally have a lower number average molecular weight.Like VM, LOFIs can be grafted with grafting materials such as, forexample, maleic anhydride, and the grafted material can be reacted with,for example, amines, amides, nitrogen-containing heterocyclic compoundsor alcohol, to form multifunctional additives.

In the present invention it may be necessary to include an additivewhich maintains the stability of the viscosity of the blend. Thus,although polar group-containing additives achieve a suitably lowviscosity in the pre-blending stage, it has been observed that somecompositions increase in viscosity when stored for prolonged periods.Additives which are effective in controlling this viscosity increaseinclude the long chain hydrocarbons functionalized by reaction withmono- or dicarboxylic acids or anhydrides which are used in thepreparation of the ashless dispersants as hereinbefore disclosed.

When lubricating compositions contain one or more of the above-mentionedadditives, each additive is typically blended into the base oil in anamount that enables the additive to provide its desired function.Representative effective amounts of such additives, when used incrankcase lubricants, are listed below. All the values listed (with theexception of detergent values since the detergents are used in the formof colloidal dispersants in an oil) are stated as mass percent activeingredient (A.I.).

MASS % MASS % ADDITIVE (Broad) (Preferred) Dispersant 0.1-20   1-8 MetalDetergents 0.1-15  0.2-9  Corrosion Inhibitor 0-5   0-1.5 Metaldihydrocarbyl dithiophosphate 0.1-6  0.1-4  Antioxidant 0-5 0.01-2.5Pour Point Depressant 0.01-5   0.01-1.5 Antifoaming Agent 0-5 0.001-0.15Supplemental Antiwear Agents  0-1.0   0-0.5 Friction Modifier 0-5  0-1.5 Viscosity Modifier 0.01-10  0.25-3  Base stock Balance Balance

Preferably, the Noack volatility of the fully formulated lubricating oilcomposition (oil of lubricating viscosity plus all additives) is nogreater than 18, such as no greater than 14, preferably no greater than10, mass %. Lubricating oil compositions useful in the practice of thepresent invention may have an overall sulfated ash content of from 0.5to 2.0, such as from 0.7 to 1.4, preferably from 0.6 to 1.2, mass %.

It may be desirable, although not essential, to prepare one or moreadditive concentrates comprising additives (concentrates sometimes beingreferred to as additive packages) whereby several additives can be addedsimultaneously to the oil to form the lubricating oil composition.

EXAMPLES The invention will now be particularly described in thefollowing non-limiting examples. Synthesis of Copolymers

Stearic acid derived 2-oxazine (20 eq.), stearic acid derived2-oxazoline (20 eq.) and propargyl tosylate (1.00 eq.) were stirred at100° C. for 30 min, 120° C. for 30 min and 140° C. until NMR showedquantitative conversion of the starting materials. Yellow or brownishsticky material were obtained and used without any further purification.The copolymer so obtained (P1) had a number average molecular weight(Mn) of 11,000 and a dispersity (Ð) of 1.34. Mn was determined by Gelpermeation chromatography (GPC) on an Agilent 1260 infinity systemoperating in DMF with 5 mM NH₄BF₄ and equipped with refractive indexdetector and variable wavelength detector, 2 PLgel 5 μm mixed-C columns(300 ×7.5 mm), a PLgel 5 mm guard column (50×7.5 mm) and an autosampler.The instrument was calibrated with linear narrow poly(methylmethacrylate) standards in range of 550 to 600,000 g/mol. All sampleswere filtered with a 0.2 μm Nylon 66 filter before analysis.

Rapeseed fatty acid derived 2-oxazoline (20 eq.), the fatty acid havinggreater than 40% of molecules having unsaturated C₁₆ to C₁₈ groups(corresponding to greater than 40% of groups R¹ in the resultingcopolymer being unsaturated and having 15 to 17 carbon atoms); stearicacid derived 2-oxazine (20 eq.) and propargyl tosylate (1.00 eq.) werestirred at 100° C. for 30 min, 120° C. for 30 min and 140° C. until NMRshowed quantitative conversion of the starting material. Yellow orbrownish sticky material were obtained and used without any furtherpurification. The copolymer so obtained (P2) had a number averagemolecular weight (Mn) of 10,100 and a dispersity (Ð) of 1.71. Mn wasdetermined by Gel permeation chromatography (GPC) in the same way as forP1.

Tests

Each of the above polymers was tested when dispersed in an API Group Ibase oil (SN15OFAW) at 0.91 wt % concentration in one or more of thefollowing tests.

-   Friction Coefficient: MTM (mini traction machine), supplied by PCS    Instruments

The test profile consisted of nine steps, alternating traction andStribeck curves, over a range of temperatures:

Step No. Step type Temperature (° C.) 1 Traction 40 2 Traction 60 3Stribeck 60 4 Traction 80 5 Stribeck 80 6 Traction 100 7 Stribeck 100 8Traction 135 9 Stribeck 135

The test parameters were as follows:

Parameter description (units) Value Load (N) 30 Stribeck step speedrange (mm/s) 2000-20  Stribeck step Slide-toRoll ratio (%) 50 Tractionstep SRR range (%)  0-60 Traction step rolling speed (mm/s) 1000 Testduration (min) 52 Disc track radius (mm) 21.05 Specimen steel grade AISI52100 Ball diameter (mm) 19 Disc diameter (mm) 46

Two or three independent repeats were carried out in a randomised trialand the results were averaged.

Viscometric Determination

-   -   Polymer concentration for viscometric determinations×1 wt % in        the same API Group I base oil (SN15OFAW) as used above.    -   HTHS (high temperature high shear) viscosity at 150°        C.-CEC-L-36-90

Results

Average Friction Example HTHS Base oil Coefficient^(a) P1 Not Gp III(Yubase 4) 0.059 measured P2 1.88 Gp I (SN150FAW) 0.036 Comp^(b) 2.62 GpIII (Yubase 4) 0.043 Base Oil 1 alone 1.80 Gp I (SN150FAW) 0.081 BaseOil 2 alone 1.52 Gp III (Yubase 4) 0.077 ^(a)Average FrictionCoefficient is calculated in the region of the Stribeck Curve from amean rolling speed of 20.1 mms⁻¹ ^(b)Comp. is a comparative test using1.00 wt % of a commercially-available olefin co-polymer dispersantviscosity modifier: HiTec 5777 in Group III (Yubase 4) base stock.

The results show that the examples of the invention (P1 and P2)exhibited friction benefits compared with the base oil tests when thecopolymers were absent. Friction performance was similar to thecommercial viscosity modifier additive at the given polymer treat ratebut significantly, the HTHS viscosity of P1 was significantly better.

What is claimed is:
 1. A lubricating composition comprising a majoramount of an oil of lubricating viscosity and 0.01 to 25 percent bymass, based on the mass of the composition of an oil-soluble copolymercomprising units (a) and units (b):—N(COR¹)CH₂CH₂—  (a)—N(COR²)CH₂CH₂CH₂—  (b) wherein the polymer carries an inorganic ororganic nucleophilic polymerisation terminating group (t), and aninitiator group (i) connected to the N atom of a repeat unit (a) or (b),the initiator group (i) being effective to initiate the polymerisationof linear, branched or cyclic hydrocarbyl moieties; and wherein R¹ andR² are the same or different and comprise a single or a mixture oflinear, branched or cyclic hydrocarbyl groups having 1-50 carbon atoms,some or all having 12-50 carbon atoms, or of at least onemacro-monomeric hydrocarbyl group with more than 50 carbon atoms.
 2. Alubricating composition according to claim 1 wherein units (a) comprisefrom 1 to 99 mol% of the copolymer and units (b) comprise from 1 to 99mol% of the copolymer.
 3. A lubricating composition according to claim 2wherein the copolymer comprises 50 mol % of units (a) and 50 mol % ofunits (b).
 4. A lubricating composition according to claim I wherein thecopolymer is a statistical copolymer or a random copolymer.
 5. Alubricating composition according to claim 1 wherein the copolymer is analternating copolymer, a periodic copolymer or a block copolymer.
 6. Alubricating composition according to claim 1 wherein the copolymer has alinear architecture.
 7. A lubricating composition according to claim 1wherein the copolymer has a branched or star architecture.
 8. Alubricating composition according to claim 1 wherein R¹ and R² are thesame or different and contain 1 to 36 carbon atoms, provided that someor all of the groups R¹ or R² have 12 to 36 carbon atoms.
 9. Alubricating composition according to claim 1 wherein the copolymer has anumber average molecular weight (Mn) of 2,000-500,000 g/mol, as measuredby Gel Permeation Chromatography with reference to linear narrowpoly(methylmethacrylate) standards in the range of 550 to 600,000 g/mol.10. A lubricating composition according to claim 1 wherein one of groupsR¹ and R² comprise unsaturated hydrocarbyl groups having between 8 and20 carbon atoms, and the other of groups R¹ and R² is saturated.
 11. Alubricating composition according to claim 1 wherein both of groups R¹and R² comprise unsaturated hydrocarbyl groups having between 16 and 20carbon atoms.
 12. A lubricating composition according to claim 1 whereinat least 5% of the total number of either or both of the groups R¹ andR² in the polymer comprise unsaturated hydrocarbyl groups having between8 and 20 carbon atoms.
 13. A lubricating composition according to claim1 wherein at least 5% of the total number of either or both of thegroups R¹ and R² in the polymer comprise unsaturated hydrocarbyl groupshaving 17 carbon atoms.
 14. A lubricating composition according to claim1 wherein at least 50% of the total number of either or both of thegroups R¹ and R² in the polymer comprise singly, doubly ortriply-unsaturated C₁₇ alkenyl groups or any mixture thereof.
 15. Alubricating composition according to claim 1 wherein either or both ofgroups R¹ and R² are obtained from natural fatty acids.
 16. Alubricating composition according to claim 1 comprising one or moreco-additives, different from the oil-soluble copolymer, selected fromone or more phosphorus-containing compounds; oxidation inhibitors oranti-oxidants; dispersants; metal-containing detergents; anti-wearagents; friction modifiers; and viscosity modifiers.
 17. A lubricatingcomposition according claim 1 comprising at least 60% by mass, of an oilof lubricating viscosity.
 18. A method of lubricating the crankcase ofan internal combustion engine comprising operating the engine andlubricating the crankcase with a lubricating composition of claim 1.